1. Field of the Invention
The present invention generally relates to a diode structure. More particularly, the present invention relates to a diode with multiple-concentric-rectangular-ring structure.
2. Description of the Prior Art
A charge pump is a kind of circuit design which is very common in a circuit system. The charge pump is able to generate an output voltage greater in magnitude than the input voltage. The charge pump is applied widely in different kind of chips. For example, a charge pump is usually integrated in an electrical erasable programmable read only memory (EEPROM), which usually needs a voltage for the programming and erasing operations higher than the voltage available from the peripheral circuit. The integrated charge pump may multiply the voltage from the circuit, to provide an appropriate voltage for the programming and erasing operations of the memory.
With the integration of the semiconductor manufacturing technology and the micro-electromechanical systems (MEMS), a semiconductor chip (biochip) which is able to detect and monitor the biological signals is developed. Generally, the electrical signal generated by an organism is very small, such as only several millivolts (mV), or even only several microvolts (μV). To detect and analyze the biological signal, a charge pump is usually integrated in a biochip to multiply the voltage of the biological electrical signal to a magnitude within the operation voltage range of the semiconductor devices embedded in the chip.
The typical charge pump circuit, for example, the Dickson Charge Pump, comprises serial connected clocked diode-capacitor voltage multipliers. By controlling the capacitors' charging/discharging cycle and the diodes' dis-conducting/conducting cycle, the charges are pumped and the total number of the charges is multiplied successively along the diode chain in the forward-biased direction, and therefore the current is multiplied. However, in real process of the charge pumping, a portion of the current would tend to flow to the substrate instead of the ideal path aforesaid when the diode is forward-biased and conducting. The current flowing to the substrate becomes the leakage current. This phenomenon would have negative influences on the efficiency of the charge pump. Therefore, there is still a need in the field to provide a diode with better performance, which has smaller leakage current and larger forward current.